Antibody to the neural cell adhesion molecule and methods of use

ABSTRACT

The present invention provides an anti-N-CAM monoclonal antibody which enhances, rather than inhibits, neurite outgrowth both in vitro and in vivo. The antibody has positive regulatory effects on nerve cells of both the central and peripheral nervous systems, and is useful for enhancing neurite outgrowth in m vitro studies and for improving nerve regeneration and repair in vivo.

This is a continuation-in-part of U.S. Ser. No. 08/018,664, filed Feb.17, 1993 (now abandoned).

FIELD OF THE INVENTION

The present invention relates to regulation of nerve growth. Inparticular, the invention relates to cell adhesion molecules whichregulate nerve growth and antibodies to such cell adhesion molecules.

BACKGROUND OF THE INVENTION

The precise and reproducible development of the nervous system invertebrates and invertebrates is accomplished by the directed growth ofaxons and dendrites (neurites) from neuronal cell bodies to theirsynaptic target cells. The extent and orientation of nerve growth isregulated and guided by a variety of molecules which are synthesized byneurons as well as non-neuronal cells. These regulators may be secretedor they may be immobilized on the surface of the cell which producesthem. Binding of the regulator to a receptor on the neuronal cellsurface causes a signal which regulates the intracellular moleculeswhich control growth. Many types of molecules which regulate neuronaloutgrowth are known. Some stimulate neurite growth (e.g., neurotrophicmolecules, neurotransmitters, extracellular matrix molecules and celladhesion molecules) while others function as inhibitors or negativeregulators. The cell adhesion molecules (CAMs) are a large group of cellsurface molecules which play an important role in regulating neuronaladhesion and neurite process extension. CAMs may be either Ca²⁺-independent (e.g., N-CAM, contactin and L1/NgCAM) or Ca²⁺ -dependent(e.g., the cadherin protein family). Several of the Ca²⁺ -independentCAMs have been sequenced, and are structurally homologous toimmunoglobulins. They are believed to mediate cell-cell adhesion by bothhomotypic and heterotypic binding mechanisms, and several are localizedon the surfaces of axons during development. As several of the Ighomologues have been demonstrated to directly stimulate neuriteoutgrowth, this group of molecules is believed to play an important rolein this process.

Of particular interest is the neural cell adhesion molecule, N-CAM,which serves as a ligand for homophilic adhesion between cells. N-CAM isgenerally recognized as a positive regulator of neuronal processoutgrowth and is present in the membranes of developing neural cells anddifferentiated axons. Adult nerves, which normally express the adult Aform of N-CAM. revert to expression of large amounts of the embryonic Eform of this molecule upon injury. Antibodies to N-CAM have been shownto reduce the outgrowth of central and peripheral axons in vitro (B. R.Seckel. 1990. Muscle & Nerve 13:785-800), and to disrupt reinnervationand functional recovery in transected sciatic nerves in vivo, presumablydue to blockage of N-CAM binding (L. G Remsen, et al. 1990. Exp. Neurol.110:268-273).

When a nerve is severed the regions of the neurites which are distal tothe break become separated from the nerve cell body and degenerate.Death and degeneration of the neurites leaves only the empty nervesheath and this, too, eventually degenerates. In addition there is somedegeneration of the proximal stump If degeneration does not result inthe death of the nerve cell body it is possible for the nerves toregenerate by re-extension of the severed axons especially if theregeneration occurs at a sufficient distance from the nerve cell body,The newly regenerating neurites are referred to as "nerve sprouts" andgrow distally toward the sheath of the distal portion of the severednerve. If the neurites successfully enter the sheath they will oftengrow down its length and function may be restored. Regrowth of theneurites is impeded or prevented by scar formation, which may bestimulated by trauma caused by suturing nerve ends in an effort tomaintain alignment or by other manipulations involved in nerve repair.Nerve guide repair, which uses a conduit to bridge the gap between theproximal and distal ends of the severed nerve, has provided analternative to nerve grafting and conventional repair techniques. Nerveguide repair is also referred to as "entubulation repair." Originally,entubulation repair employed an empty plastic tube applied to thedamaged nerve ends to guide regrowth. With this technique there is lesstrauma, as only one epineural suture in each nerve stump is usuallyrequired to hold the nerve guide in place. Nerve guide repair may alsoprevent or reduce ingrowth of scar tissue which may interfere with thedistal migration of the nerve sprout. The proximal stump, suspended inthe nerve guide, may therefore begin its distal migration withoutobstruction by an imperfectly aligned degenerating distal stump, scartissue, etc.

As certain cell adhesion molecules (CAMs, e.g., N-CAM, L1 Antigen,N-cadherin, GP135), neurotrophic Factors (i.e., factors which promotesurvival and growth of neurons such as NGF and CNTF), andneurite-promoting factors (i.e., substrate bound glycoproteins which areusually components of the basal lamina such as laminin, collagen,entactin proteoglycan, fibrinogen and fibronectin) have been found to beinvolved in peripheral nerve regeneration, they have been used to modifynerve guides to improve nerve repair. Madison, et al. (1988. BrainResearch 447:325-334) describe a nerve guide having a lumen filled witha collagen- or laminin-containing gel. U.S. Pat. No. 5,019,087 disclosesa nerve guide having walls comprising Type I collagen or laminin. U.S.Pat. No. 5,011,486 discloses nerve guides comprising porous tubularmembranes having a growth-enhancing active factor incorporated withinthe membrane. U.S. Pat. No. 4,759,764 discloses the use of basal laminawith the cellular material removed as a nerve guide. U.S. Pat. No.4,955,892 discloses addition of a neural cell adhesion molecule (N-CAM)to a matrix in the lumen of the guide. While N-CAM enhances nervegrowth, antibodies to N-CAM reportedly disrupted recovery of musclefunction when nerve guides containing such antibodies were applied totransected sciatic nerves (L. G. Remsen, et al., supra). US. Pat. No5,026,381 discloses a nerve guide with multilayered, semipermeable wallscomprising Type I collagen.

In the tubular nerve guides described in the prior art, the regeneratingaxons grow along the inside wall of the tube, along other axons, oralong Schwann cells which have previously bridged the gap between thestumps. It is therefore likely that the axon will lose positionalinformation and waste energy by growing in nonproductive directions, asa large surface area is available for regrowth. This problem can beovercome by providing a nerve guide in the form of a fiber (i.e., afiber nerve guide) which presents less surface area to the regeneratingaxon. The neurite therefore has less opportunity to lengthen its path tothe target distal stump or sheath, resulting in more efficientregeneration. The fiber may be a surgical suture which is used to join anerve bundle or fasicle of one stump of a severed nerve to thecorresponding bundle of the other stump. Alternatively, the fiber nerveguide may be used in vitro to guide nerve cell outgrowth, in which casenerve cells may be placed on the fiber either as a mass of cells (e.g.,a ganglion) or as dissociated cells useful for studies of individualnerve cells. A molecule which regulates neuronal process (nerve sprout)outgrowth may be applied to the surface of the fiber, i.e., layeredthereon or covalently coupled to the fiber, to promote and direct thisprocess.

SUMMARY OF THE INVENTION

The present invention provides an anti-N-CAM monoclonal antibody whichenhances, rather than inhibits, neurite or neuronal process outgrowthboth in vitro and in vivo. The antibody has positive regulatory effectson nerve cells of both the central and peripheral nervous systems, andis useful for enhancing neurite outgrowth in in vitro studies and forimproving nerve regeneration in vivo.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the data generated in Example 2 comparing theperformance of fiber nerve guides having different neuronal regulatorymolecules on the surface.

FIG. 2 is a graph of the data generated in Example 3 comparing theperformance of fiber nerve guides having different neuronal regulatorymolecules on the surface.

FIG. 3 is a graph of the data generated in Example 4 comparing theperformance of fiber nerve guides having different neuronal regulatorymolecules on the surface.

FIG. 4 is a graph of the data generated in Example 5 comparing theperformance of NCAM16.2 to a control antibody in vivo.

DETAILED DESCRIPTION OF THE INVENTION

Leu19, an anti-NCAM monoclonal antibody (Becton Dickinson AdvancedCellular Biology. San Jose. Calif.) was used to prepare animmunoaffinity column. NCAM from human adult brain was purified bystandard techniques using the Leu19 affinity column. Using conventionaltechniques for preparation of monoclonal antibodies, mice were immunizedwith the immunoaffinity purified NCAM and the spleen cells were fusedwith murine myeloma cells. The hybridomas produced were screened forreactivity with the immunogen in ELISA assays and rescreened withsynthetic peptides representing various immunoglobulin domains of NCAM.The hybridoma which produces NCAM16.2 was selected for furthercharacterization based on its strong reactivity with the immunogen, andwas deposited with the American Type Culture Collection (Rockville, Md.)under the Budapest Treaty on Feb. 2, 1993 under Accession No. HB11261.This antibody is also commercially available from Becton DickinsonAdvanced Cellular Biology (San Jose, Calif.

Several of the monoclonal antibodies isolated were characterized fortheir effects on neurite outgrowth. Rat cerebellar neurons (CNS) and ratdorsal root ganglia (PNS) were tested for their growth response tomonoclonal antibodies NCAM16.2, NCAM14.2 and NCAM18.1, either with orwithout bound NCAM antigen. The antibodies were bound to plastic platesderivitized groups for coupling to oxidized sugars on glycoproteins(AVIDPLATE-HZ, BioProbe, Inc.). Antigen, if bound to the antibody, wasapplied for 1 hr. at 10 μg/ml after blocking the plate with BSA-TBST (1%bovine serum albumin in TRIS---buffered saline containing 0.05%TWEEN-20). After rinsing with PBS, the antigen was crosslinked to theantibody with glutaraldehyde for 0.5 hr., followed by an additionalblock with BSA-TBST. The plate was sterilized with three washes withHBSS and Pen-Strep. Neurite outgrowth in the wells containing antibodyonly was substantially equivalent to that in the buffer-only controlwell for all monoclonal antibodies except NCAM16.2. In the presence ofNCAM1.62, extensive neurite outgrowth was seen in cerebellar cells afteronly 24 hrs., with large numbers of neurite processes reaching forconsiderable distances. The outgrowth-promoting effect of NCAM16.2 ondorsal root ganglion cells was smaller, but still clearlydistinguishable over the other antibodies and from the buffer-onlynegative control. Similar effects were seen in crosslinked controlswhere no antigen was present and under conditions where the antigen wasnot crosslinked (e.g., antigen was removed by washing). Neuriteoutgrowth was totally inhibited when NCAM16.2 was crosslinked to itsantigen by glutaraldehyde or DMP (dimethyl pimelimidate--Pierce). Overtwo additional days of growth, the cells treated with NCAM16.2 continuedto produce extensive neurite processes, whereas those treated with theother anti-NCAM antibodies showed little, if any, neurite outgrowth.

Characterization of the epitopes recognized by the anti-NCAM monoclonalantibodies demonstrates that NCAM18.1 is directed against anintracellullar epitope and is therefore effectively a negative controlantibody when used on intact cells. The epitope recognized by NCAM16.2appears to be in the third immunoglobulin domain (Ig-3). This wasdetermined by expressing the cloned Ig domains of NCAM as LacZ fusionproteins in bacteria. After induction by IPTG, the reactivity of theantibodies with the fusion proteins was determined on Western blots.NCAM16.2 recognized the Ig-3 and Ig-3+4 fusion proteins, but did notrecognize the fusion protein containing the Ig-4 domain alone. Ig-4contains the VASE exon of N-CAM, and it is therefore unlikely thatNCAM16.2 is directed to the VASE exon specifically.

Monoclonal antibody NCAM16.2 unexpectedly promotes neurite outgrowthfrom central nervous System and peripheral nervous system cells, whereasprior art anti-NCAM antibodies functioned as antagonists or inhibitorsof nerve cell growth. This effect is seen both in vitro and in vivo,where repair of severed nerves and restoration of function may be morerapid using nerve guides or fiber nerve guides employing the inventiveantibody. In vitro, NCAM 16.2 provides a means for improving the rateand extent of neurite outgrowth, thereby shortening the time required toobtain results of experiments on nerve growth and its regulation.NCAM16.2 may also be labeled with a detectable label as is known in theart to provide a tracer antibody for detection of NCAM (and particularlythe Ig-3 domain) in cells or in cell extracts. As blocking of an epitopein the Ig-3 domain of NCAM by binding to NCAM16.2 appears to furtherenhance the growth promoting activity of NCAM, study of the regulatoryrole of this epitope is of significant interest for therapeutic use ofNCAM and NCAM16.2 in nerve regeneration. The availability of an antibodywhich recognizes this newly identified epitope of NCAM provides a toolfor conducting such studies.

The following experimental examples are provided to illustrate certainspecific embodiments of the invention and are not intended to limit theinvention as defined by the appended claims.

In Examples 1-4 rat dorsal root ganglia were prepared as follows: Dorsalroot ganglia (DRG) from embryonic, neonatal, or adult rats weredissected into sterile Hank's balanced salt solution (HBSS). The DRGwere mildly digested with collagenase (1 mg/ml) and hyaluronidase (0.5mg/ml) for 15-20 min. at 37° C. Embryonic and neonatal DRG were squeezedonto sutures. For adult DRG the coated suture was sewn through theganglia. The DRG were grown in medium at 37° C. and observed atintervals. The proteins used as substrates for neurite outgrowth wereobtained as follows: Human laminin and bovine serum albumin (BSA) werepurchased from Sigma Chemical Company (St. Louis, Mo.). Mouse monoclonalantibody (MAb) NCAM16.2 was purified on Protein A-Sepharose. Human celladhesion molecules (N-CAM, L1-Antigen and contactin) were purified fromadult brain tissue by immunoaffinity chromatography on the appropriateimmobilized MAb.

The proteins were covalently coupled to the nylon sutures as follows:Method 1 (acid hydrolysis)--Suture grade nylon, three-ply, size 10:0,was purchased from Ashaway Line and Twine (Ashaway, R.I.). It washydrolyzed with HCl to generate free amino groups and reacted withglutaraldehyde to yield an activated nylon (see Hornby and Goldstein.1976. Meth. Enzymol. 44:121). In an additional, optional step, theactivated nylon was reacted with polyacrylamide hydrazide to yield nyloncontaining multiple reactive groups. Proteins to be coupled wereoxidized with sodium periodate and dialyzed against 50 mM sodium acetatepH 4.5. The oxidized proteins were incubated with the activated nylonovernight at 4° C. Remaining active sites were blocked with 1% BSA inTBST for 3 hr. at room temperature. The derivatized and blocked fiberswere then washed several times with sterile HBSS containing penicillinand streptamycin before use. Method 2 (O-alkylation)--Nylon as in Method1 was O-alkylated and reacted with adipic dihydrazide to generatereactive hydrazide groups (1976. Meth. Enzymol. 44:122). Proteins werecoupled and blocked as above. Method 3 (O-alkylation withpolyacrylamide)--Nylon was O-alkylated as in Method 2 but the fiberswere then reacted with polyacrylamide hydrazide instead of adipicdihydrazide to generate multiple hydrazide groups for reacting withoxidized protein.

In Examples 1-4 neurite outgrowth was estimated by observing thecultures under the microscope and estimating the percent of the totalfield covered.

EXAMPLE 1

To compare the growth promoting effects of NCAM16.2 to known positiveregulators of neuronal outgrowth, day 2 postnatal (P2) rat DRG weremildly digested and squeezed onto sutures. The growth medium was changedon day six of culturing. Method 1 was used to couple the regulatorymolecules and factors to the sutures. The results of the experiment aresummarized in the following Table:

    ______________________________________                                                     NO. OF                                                           PROTEIN COAT GANGLIA    RESULTS                                               ______________________________________                                        BSA          1          day 2                                                 little outgrowth                                                                                      day 5                                                 0.5 mm                                                                                                day 7                                                 0.5 mm                                                                                                day 14                                                1.5 mm                                                                        Contactin    1          day 2                                                 sig. outgrowth                                                                                        day 5                                                 0.5-2.0 mm                                                                                            day 14                                                2.5 mm                                                                        Mab NCAM16.2 3          day 2                                                 some outgrowth                                                                                        day 7                                                 2.0-3.0 mm                                                                                            day 14                                                3.5-5.0 mm                                                                    ______________________________________                                    

As early as day 5, the sutures coated with a positive protein regulatorof neurite outgrowth (contactin) and an antibody to a positive regulatorof neurite outgrowth (Mab NCAM16.2) showed increased outgrowth ascompared to sutures coated with BSA. Mab NCAM16.2 was unexpectedly foundto be superior to contactin for increasing the rate of outgrowth.

EXAMPLE 2

Positive regulators or neurite outgrowth were compared using analternative covalent coupling method. Postnatal day 0 rat DRG weresqueezed onto nylon sutures prepared according to Method 2(O-alkylation). The results were as shown in the following Table.Outgrowth measurements represent the average of multiple suturesprepared with each coating:

    ______________________________________                                                     DAY 4         DAY 5                                                           OUTGROWTH     OUTGROWTH                                          PROTEIN COAT (mm)          (mm)                                               ______________________________________                                        Laminin      0.8           1.4                                                BSA          0.6           0.8                                                L1 Antigen   0.9           1.4                                                MAb NCAM16.2 2.6           3.2                                                Contactin    0.9           1.4                                                N-CAM        2.0           2.2                                                No protein   0.7           0.8                                                ______________________________________                                    

All sutures coated with positive regulators showed increased rates ofneurite outgrowth as compared to BSA coatings and uncoated sutures. Thedifferences were most pronounced at Day 5. At Day 4 laminin, L1 antigenand contactin showed measurable but only minimal improvement. However,by Day 5 these same molecules promoted significantly increased neuriteoutgrowth. Again, however, the extent of outgrowth was significantlyhigher at both day 4 and day 5 on sutures coated with NCAM16.2 than onsutures coated with the conventional positive growth regulators. Theresults are depicted graphically in FIG. 1.

EXAMPLE 3

Late embryonic rat DRG were squeezed onto nylon sutures preparedaccording to Method 2 (O-alkylation). The results for neurite outgrowthrates are shown in the following Table and depicted graphically in FIG.2:

    ______________________________________                                                   DAY 1    DAY 4    DAY 7  DAY 19                                               (mm)     (mm)     (mm)   (mm)                                      PROTEIN    AVG.     AVG.     AVG.   AVG.                                      COAT       (S.D.)   (S.D.)   (S.D.) (S.D.)                                    ______________________________________                                        Laminin    0.5 (0.1)                                                                              1.8 (1.5)                                                                              1.3 (1.2)                                                                            4.1 (1.2)                                 BSA        0.1 (0.1)                                                                              0.1 (0.1)                                                                              0.1 (0.1)                                                                            1.0 (1.7)                                 L1 Antigen 0.4 (0.2)                                                                              1.1 (0.8)                                                                              2.4 (1.3)                                                                            5.6 (1.9)                                 MAb        0.8 (0.4)                                                                              0.8 (0.7)                                                                              1.5 (1.0)                                                                            4.9 (2.1)                                 NCAM16.2                                                                      Contactin  0.4 (0.2)                                                                              1.2 (0.9)                                                                              2.4 (0.4)                                                                            4.1 (1.3)                                 N-CAM      0.4 (0.2)                                                                              0.8 (0.2)                                                                              1.5 (0.6)                                                                            4.2 (1.4)                                 ______________________________________                                    

As early as Day 1 of culture, neurite outgrowth on sutures coated withpositive regulators was significantly improved as compared to outgrowthon BSA coated sutures. Again, the antibody directed against NCAMunexpectedly also provided increased rates of neurite outgrowth. Thepositive effect of NCAM16.2 was more comparable to that of conventionalpositive regulators in this study, and may reflect differences inbiological activity on embryonic nerve cells as compared to postnatalnerve cells.

EXAMPLE 4

Adult rat DRG were prepared and the sutures sewn through. Regulatoryproteins were coupled to the sutures using Method 2 (O-alkylation).Results were as shown in the following and are depicted graphically inFIG. 3:

    ______________________________________                                        PROTEIN     DAY 5   DAY 7     DAY 9 DAY 14                                    COUPLED     (mm)    (mm)      (mm)  (mm)                                      ______________________________________                                        Laminin     0.4     0.4       0.5   2.9                                       BSA         0.0     0.2       0.2   0.6                                       L1 Antigen  1.8     2.1       2.5   6.2                                       MAb         1.6     2.0       2.5   8.0                                       NCAM16.2                                                                      None        0.9     1.3       1.5   2.7                                       ______________________________________                                    

In this experiment laminin provided no outgrowth advantage over uncoatedsutures. However. L1 Antigen and MAb NCAM16.2 significantly acceleratedneurite outgrowth as compared to tile controls. The NCAM16.2 effect onoutgrowth was significantly more pronounced than that of L1 antigen byday 14. The sutures which had no coupled protein were prepared throughthe activation step of Method 2. Comparison of the activated sutures tothe BSA coated sutures shows that activation itself improved the rate ofneurite outgrowth, even in the absence of a nerve regulatory factor.

EXAMPLE 5

The rat sciatic nerve model was used to determine whether NCAM16.2 alsohas positive effects on the rate and extent of nerve regeneration invivo. The protocol was generally as described by P. G. Cordeiro, et al.(1989. Plastic and Reconstructive Surgery 83:1013-1020). The sciaticnerve of adult male Fisher 344 rats was transected unilaterally atmid-thigh level and a 5 mm section of the nerve was removed The nervewas repaired with a 10 mm polyethylene tube filled with one of twoantibodies (an anti-Chlamydia control antibody and NCAM16.2, 10 animalseach).

Animals were sacrificed two weeks after tube implantation and the tissuewas processed as follows to display the number of myelinated axons atmid-tube level. Under deep Detamine anesthesia the animals weretranscardially perfused with heparinized phosphate buttered saline (pH7.2), followed by 1% glutaraldehyde and 2% paraformaldehyde in 0.1Mphosphate buffer (pH 7.2). The sciatic nerve, including the entubulationrepair, was exposed between the sciatic notch and the popliteal fossaand removed over a length of 1.5 cm distally from the sciatic notch.Post fixation was performed in 2% glutaraldehyde in 0.1M phosphatebuffer (pH 7.2) for 24 hrs. at 4° C., followed by 2% osmium tetroxide in0.1M phosphate buffer for 2 hrs at room temperature. The tissues wereembedded, with propylene oxide as the intermediate solvent, in Epon 812resin. Sections were cut for light microscopy from the central region ofthe regenerated nerve cable that had formed within the entubulationrepair. One micron transverse sections were cut and stained withtoluidine blue and examined with a Zeiss Axiophot light microscope.

The number of myelinated axons was determined using a computer-basedmorphometric system. Images were digitized using a Macintosh based videodigitizer and the Image 1.4 image analysis program (NIH) Thecross-sectional area and thickness of the perineural layer were measuredfor each regenerated cable. Myelinated axons were counted within 62.3 μmby 47.5 μm sectors (total area=2960.5 μm²) in a 47.5 μm wide centrallylocated band across each regenerated cable Maturation and remyelinationof the regenerated axons occur at the greatest rate within the core ofthe regenerated cable. The area of the regenerated cable containingremyelinated axons increases over time and is eventually limited by theperipheral boundary of the "perineural" layer. For accuracy, methods forestimating the population of myelinated axons within the cable shouldaccount for the myelinated axons occurring within a limited region ofthe total cable cross-sectional area. The method employed in this studyused the number of sampling frames in which myelinated axons aredetected to estimate the diameter (in number of frames) of the centralarea containing myelinated axons. The myelinated axon density wascalculated by dividing tile total number of axons observed by the numberof frames in which axons were detected, resulting in the number ofmyelinated axons/sample frame (axons/2960.5 μm²). From the myelinatedaxon density and the area of the central myelinated axon containingregion, the total number of myelinated axons was estimated. Differencesamong groups were analyzed using an unpaired t-test as well as aWilcoxon signed-rank test.

The results are shown in FIG. 4. There were significantly more axons inthe group of animals which received NCAM16.2 than in the control(p<0.05). Approximately 55% of the control animals did not display anymyelinated axons at the two week time point vs. only 30% of the animalsreceiving NCAM16.2. This study was designed to evaluate the very earlystages of regeneration, and the results show a clear stimulatory effectof NCAM16.2 on initial axonal outgrowth. The in vivo study complementsthe in vitro studies and shows that in this model system NCAM16.2significantly enhances early axonal regeneration across a 5 mm nerve gapdistance. These results also suggest that NCAM16.2 may enhance bridgingof even longer nerve gap distances, making this antibody useful forimproving nerve regeneration in primates where nerve gap distances of5-10 cm are not uncommon.

What is claimed is:
 1. Monoclonal antibody NCAM16.2.
 2. The antibody ofclaim 2 labeled with a detectable label.
 3. A tubular nerve guidecomprising a lumen filled with a composition comprising monoclonalantibody NCAM16.2.
 4. A fiber guide comprising monoclonal antibodyNCAM16.2 covalently coupled to the fiber nerve guide.
 5. Hybridoma ATCCAccession No. HB11261.
 6. Monoclonal antibody NCAM16.2 produced byhybridoma ATCC Accession No. HB11261.